Frequency-based analysis of diastolic function

Quantitative determination of the filling (diastolic) function of the heart has been primarily correlative rather than causal and has been thwarted by the inability to define sensitive and specific non-invasive numerical indexes. In analogy to impedance, Z(ω)=V(ω)/I(ω) relating voltage V to current I in circuit theory, we introduce the concept of frequency-based analysis of diastolic function (DF) by analyzing the left ventricular (LV) filling pressure (P) to flow(Q) relation in terms of impedance as, Z(ω)=P(ω)/Q(ω). This allows abnormal DF to be viewed as a state of impedance mismatch between pressure and flow, relative to normal. Simultaneous pressure-flow data in 11 subjects was recorded during catheterization. Analysis of variance between groups (ANOVA) shows that the direct current (DC) component of impedance, Z₀ and the first harmonic coefficient, Z₁, differentiated between normal and abnormal DF groups (p<0.05). We conclude frequency-based analysis of DF differentiates between normal and abnormal DF states, elucidates the physiology of normal filling as a low-pass filter and has potential as a method for noninvasive DF quantitation.